Designed to add warmth to your sleeping bag and protect it from dirt and sweat, the Snugpak Thermalon and fleece liners provide year-round comfort in the backcountry. With a blanket-like cut that can be used inside a sleeping bag or as a light summer blanket, the Thermalon adds up to 10 degrees of warmth to your sleeping bag. The fleece liner features a mummy-sack design, as well as a full-length zipper, and adds up to 15 degrees of warmth. Both liners are moisture wicking and come with a compression stuff sack, so you can pack them into a backpack.